A large cock. This phrase was popularized by the Sean Paul song of the same name featuring Wayne Marshall. Yardi refers to locals, or sometimes jail-cell pals (as in "jail yard"). Double entendre here since yardie also can mean one yard long, i.e. a 36-inch monster boner.

A slang term for the penis of a jamaican man.
The implication being that a 'yardie bone' is large ('yardie' refers both to the slang term for jamaicans as well as a shortening of 'yard stick' which implies lenght) and if Sean Paul is to be believed; superior to say caucasian bone.
See 'yardie' for its definition.

"girls from all over the world call on my cell, because they know the yardie boys do it well. Its a well known fact, if dem get the yardie bone then they must come back"
- Sean Paul ('yardie bone' song)